- 1 year ago
BaseOfCode present in PE+ executable
In a PE+ (Portable Executable Plus) executable, the BaseOfCode
field is part of the IMAGE_OPTIONAL_HEADER structure within the PE header. This field specifies the virtual address of the starting point of the executable code section in memory.
The PE+ format, also known as PE64 or PE32+, is an extension of the traditional PE (Portable Executable) format used on 64-bit versions of Windows. It supports 64-bit memory addressing, allowing the executable to utilize larger address spaces and support larger executable files.
Here is the definition of the IMAGE_OPTIONAL_HEADER
structure from the Windows SDK:
ctypedef struct _IMAGE_OPTIONAL_HEADER64 {
// ... (Other fields omitted for brevity)
DWORD BaseOfCode; // The RVA (Relative Virtual Address) of the code section
// ... (Other fields omitted for brevity)
} IMAGE_OPTIONAL_HEADER64, *PIMAGE_OPTIONAL_HEADER64;
In a 32-bit PE executable (PE32), the BaseOfCode
field is part of the IMAGE_OPTIONAL_HEADER32
structure.
The BaseOfCode
field is crucial for the operating system's loader, as it indicates where the code section should be loaded in memory when the executable is executed. The loader maps the executable's code section into the virtual address space of the process at the specified RVA.
It's important to note that the BaseOfCode
field is a relative virtual address (RVA) and not an absolute address. The absolute virtual address where the code section will be loaded is determined by the loader based on the preferred base address specified in the ImageBase
field of the optional header.
In summary, the BaseOfCode
field in a PE+ executable specifies the RVA of the code section, which is essential for the loader to map the code section into memory when the executable is executed.